1. Field of the Invention
The present invention relates to a compressed air strainer and drying treatment. More particularly, the present invention is directed to an air strainer connected to a heat-exchanger. The compressed air is depurated by water and pills piled on baffle plates in the strainer, so that oil, dirt and other contaminants are filtered out from the raw air. Then, the moist clean air flows into the heat-exchanger to remove heat therefrom. Next, the air is output into an evaporator to be evaporated to dry the air, producing condensed water and dry clean air. The condensed water and the dry clean air are separated in a splitter, so that the condensed water flows back into the air strainer through a U-shaped pipeline. The high-purity air is made available at the outlet. The contaminants in the air strainer can be drained out with some of the water automatically or manually so as to keep the filtering medium cleaning without being fully replaced.
2. Prior Art
In accordance with modern manufacturing methods, and for the sake of lower cost, compressed air is utilized widely for operating and controlling pneumatic tools, and providing cooling, drying, cleaning, conveying and packing of professional machines, and is used for painting, decorating surface instruments and precision equipment. Therefore, high quality compressed air is now required. Because the outside air is directly drawn into the air compressor, with dirt and contaminants being drawn in together with the air. The compressor adds a lubricant to the air. The compressed air output from the air compressor, therefore, contains an oil mist, dirt, contaminants and moisture. Due to this poor quality of compressed air output, without being processed by filtering and drying treatments, the service life of the machines using the compressed air is affected.
Referring to FIG. 1, a conventional compressed air filtering and drying system is shown. An outlet of a compressor 1 connects to an air reservoir 2, and an inlet of a conventional cooling and drying apparatus 4 is linked to another port of the air reservoir 2. The outlet port of the conventional cooling and drying apparatus 4 connects to an inlet of a filter 3, and the outlet of the filter 3 provides a connecting port for connection of a pipeline, to output clean compressed air for use. As mentioned above, the poor quality air, the oil mist, dirt and contaminants carried by the air entering the air cooling and drying apparatus, will directly and seriously affect the operating efficiency and the service life of the air cooling and drying apparatus. After passing through the cooling and drying apparatus, the compressed air is purified by the filter 3 for improving the quality of air. But, after undergoing a long period of usage, the inside strainer core of the filter will be gradually blocked, restricting the flow of compressed air therethrough.
Referring additionally to FIG. 1A, the air cooling and drying apparatus includes a compressor 10, a fan motor 11, a condenser 12, a cold-producing medium filter 13, a capillary 14, an evaporator 15, a cold-producing medium return conduit 16, a hot-gas by-passing valve 17, an evaporation manometer 22, an air inlet 19, a splitter 21, an air outlet 20, an air exit manometer 23 and an automatic drainer 18. The cold-producing medium loop employs the compressor 10 to circulate the cold-producing medium via the condenser 12, the cold-producing medium filter 13, and the capillary 14 to the evaporator 15. The evaporator 15 is thereby cooled and heat is exchanged from the outside air. Then, via the cold-producing medium return conduit 16, the cold-producing medium flows back to the compressor 10 to finish one cycle. The cold-producing medium evaporation manometer is coupled to the front end of the cold-producing medium return conduit 16 for indicating the change in pressure of the cold-producing medium in the evaporating process. Meanwhile, a hot-gas by-passing valve 17 bridges between the outlet of the compressor 10 to the return conduit 16 for controlling the temperature of the cold-producing medium. The air loop makes use of the compressed air flowing into the evaporator 15, through the air inlet 19, for exchanging heat with the cold-producing medium. By means of the cooling effect of the evaporator 15, water will be condensed from the raw compressed air and cold dry air will result. Then, the condensed water is separated with the cold dry air by the splitter 21, and drained out automatically by the automatic drainer 18. Meanwhile, the cold dry air separated by the splitter is output via the air outlet 20. But, the oil mist carried in the compressed air sticks on the surface of the cold-producing medium pipelines in the evaporator 15 to form a coating, and detrimentally affects the heat exchange process, so that the heat-exchange efficiency goes down greatly.
Referring to FIG. 2, a conventional strainer, shown on the drawing, is made of a circular filter screen 24 at the core, an adhesive-bonded fabric layer 25 covering the outside of screen 24. Next, a glass fiber layer 26 is wrapped on the layer 25. Lastly, another filter screen 27 is wrapped fully around the other layers in order to block and stick the oil mist and dirt on the every layer's surface for, filtering out the clean air from the oil mist and dirt. But, along with increasing the period of usage, the oil mist and dirt attached on the filter screen piles up. Therefore, the resistance to passage of the compressed air passing through the filter screen 24 increases. If the filter screen 24 is not replaced in time, the pressure difference will rise to a level where the filter screen becomes distorted, followed by it breaking up and thereby causing the filter to lose its effectiveness.
Accordingly, the conventional compressed air filter and drying treatment have shortcomings as follows.
1. Due to the filter core of the filter consisting of a filter screen, an adhesive-bonded fabric and glass fiber, it cannot endure highly moist and higher temperature compressed air. Degradation of the filter inner core by deposition of water and destruction of the composition of the filter material by high temperatures are hard to avoid. Therefore, this kind of filter is not suitable for coupling to the inlet of the air cooling and drying apparatus for prefiltering. So, the poor quality compressed air must be directly input into the air cooling and drying apparatus will thus be a menace to the service life of the air cooling and drying apparatus. PA1 2. When the conventional air cooling and drying apparatus processes the raw compressed air, due to a lack of pre-filtering to remove the oil mist, the oil mist will stick to the surface of the cooling medium, to form an oil coating end thereby isolating the pipeline from the compressed air, the heat-exchanging efficiency is seriously affected. PA1 3. Along with an increase in usage time, a gradual obstruction of the filter core develops, so that the air flow rate is decreased or becomes unstable. PA1 4. If the obstruction of the conventional filter core is so serious that, beside increasing the pressure difference of the compressed air, the filter core becomes distorted under the high pressure, if the filter core will break-up and the effectiveness of filter will be lost. PA1 5. Because the oil and dirt that sticks to the filter core cannot be automatically removed, the user must pay careful attention on the frequency of filter core changes. Judging when the filter core should be replaced or whether it has or becomes a big problem and bother for the user. PA1 6. The filter has to be replaced often, but frequency replacing of the filter core not only increases the production cost, but also pollutes the environment with the abandoned filter cores.